Priming of CPB Circuit

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INTRODUCTION
 To replace the air in the circuit with fluid or blood.
 To fill the circuit
 To check the circuit for leaks or damage
 To test the pump and circuit
 Priming with fluid reduces the blood dependence.
 Primingfluid causes hemodilution.
 Hemodilution can be beneficial/ harmful.

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NECESSITY TO USE HAEMODILUTION
 Homologous Blood Syndrome
 Shortage and cost of blood
 Oxygenators were inefficient.
 Hemodilution increased their efficiency
 To reduce the harmful physiological effect
 of blood going through the pump

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ADVANTAGES OF HEMODILUTION
 Decreases blood viscosity
 Improves regional blood flow
 Improved oxygen delivery of tissues.
 Decreased exposure to blood products.
 Improved blood flow at lower perfusion
pressures during hypothermia.
 Decreases bypass related
complications(neurologic, renal and pulmonary)
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DISADVANTAGES OF HEMODILUTION
Extreme hemodilution can cause

 1. Decrease in oxygen carrying capacity

 2. Tissue oedema in various organs
 3. Reduces neuro congnitive outcomes
 4. Increases the distance between capillaries
and tissues causing tissue necrosis and cell
damage
 5. Can cause mortality and morbidity
 6. Increases lung fluids after CPB
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EFFECTS OF HAEMODILUTION

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RELATIONSHIP OF VISCOSITY TO PRESSURE DROP

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2. Effect on Oxygen Transport

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3. EFFECT ON HAEMATOCRIT

 Predicted HCT on bypass (C2)=

Patients blood volume before CPB (V1) x pre CPB Hct (C1)
Patients blood volume before CPB + CPB prime (V2)
Volume concentration formula
V1 x C1 = V2 x C2
 V1 is patient blood volume
 V2 is total volume(Prime + blood Volume) on CPB
 C1 is patient haematocrit
 C2 is required Haematocrit on CPB

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 C1 = 30 %
 V1 = weight x 70 (Male), 60 (Female) 80 (Child)
 Weight = 70 kg
 C2= Required HCT = 25%
 V2= ?
 Prime Volume=?

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PRIMING SOLUTIONS CLASSIFICATION

 CRYSTALLOIDS : fluids with smaller solutes

and lesser atomic weights. Remains in the
circulation for smaller time ( 15 mts) eg: Ringers
soln, Dextrose etc
 COLLOIDS : Fluids with bigger solutes and
greater atomic weight. colloids contain larger
They help in the preservation of oncotic pressure.
Eg : Hemacell, Albumin etc
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Most commonly used primes

 Balanced Salt solutions

 Colloids (Hestril, albumin, plasma & blood)
 Mannitol
 Heparin
 Bicorbonate as buffer

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THREE TYPES OF CRYSTALLOIDS:

1. Hypertonic crystalloid:
a higher concentration of electrolytes than the body plasma(Causes to shift
from the extravascular spaces to the intravascular space).
2. Hypotonic crystalloid:
a lower concentration of electrolytes than the body plasma(Causes water to
shift from the intravascular space to the extravascular space).
3. Isotonic crystalloid:
the same concentration of electrolytes as the body plasma [not causing a
significant shift of water between the body compartments
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CRYSTALLOIDS

1. Dextrose
2. Plasma-Lyte
3. Ringer's (Hartmann)
4. mannitol
 volume expanding solutions
 mimic the normal plasma electrolyte concentrations
 effective hemodilution but they lack oncotic activity.
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Advantages of Crystalloids Solutions

 Easily mixed and dissolve in a solution.

 Ability
to transit across the semipermeable
membrane
 Mobility from bloodstream into cells and body
tissues.
 Ability may increase the fluid volume in both
interstitial and intravascular spaces.
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1-Dextrose:

 5% Dextrose in Water is isotonic and acidotic(pH

5.0).
Beneficial Effects
1. Reducing The Mechanical Damage To Erythrocytes
2. Improving Intraoperative And Postoperative
Diuresis.
3. Decreased Peri-operative Fluid Requirement
4. Reduced Postoperative Fluid Retention . 17
Disadvantages of using dextrose

1- may cause systemic metabolic acidosis.

2- may increase the level of blood glucose, especially in diabetic

patients.

3- Possibility of increase the risk of neurological complications of

cardiopulmonary bypass.

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2-Balanced crystalloid fluids:

 Balanced crystalloids are fluids that have a

neutral pH Plasma-Lyte solution (pH 7.4), or
slightly low pH (slightly acidotic) Ringer's
(pH 6.6),
 isotonicand consist of electrolyte ions
approximately similar to that of human
plasma.
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Ringer's lactate, or Hartmann's
(Ringer's solution)
 Typical Example Of A Balanced Crystalloid.
 Lactate As A Source Of Bicarbonate.
 LactateMay Be Converted Into Glucose In
Vivo Through The Gluconeogenic Pathway, As
Result Of That We Must Be Careful When
Using A Large Volume Of Fluid Containing
Lactate In Diabetic Patients.
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Plasma-Lyte solution

 Contains acetate and gluconate for bicarbonate

production,
 Magnesium which is important in cellular process of
energy transfer and in myocardial ATP metabolism..
 The balance in Ringer's lactate or Plasma-Lyte is
resulting from metabolizing of lactate (In Ringer's
lactate) and acetate(In Plasma-Lyte). Both lactate
and acetate are ultimately metabolized to bicarbonate
in the liver. 21
 3-Mannitol:
 hypertonic, acidotic (pH 4.5 –7.0)
 low molecular weight (182 Da) crystalloid.
 clinical practice to stimulate diuresis.
 volume expander, initially it draws the fluid across the capillary to the plasma.
 Mannitol diffuses rapidly into the interstitial fluid and draws water from the body cells to
extracellular phase, resulting increase in the volume of the extracellular phase or
compartment.
 protective effect on renal function
 a beneficial effects on all organs, including the brain and heart.
 Commonly used with circuit prime of cardiopulmonary bypass.
 administered is 0.5-1 g/kg .
 The diuretic effect of mannitol continue for up to 12 h. It is classified as an osmatic
diuretic. 22
Colloid solutions
 Large proteins
 High molecular weight substance (generally MW > 30,000 da)
 Stay within the vascular space (blood vessels)
 Greater than crystalloids
 Do not pass across capillary walls as easily as crystalloids.
 Colloid osmotic pressure (Oncotic pressure) is a form of
osmotic pressure exerted by proteins or other high molecular
weight substance in a blood vessel's , that usually tends to pull
water from extravascular spaces to the Intravascular spaces . It
is the opposing force to capillary filtration pressure and
interstitial colloidal osmotic pressure . 23
Colloids solution types

 1- Natural( human albumin).

 2- Artificial(dextran solutions, gelatin, and HES).

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1-Albumin:
 The Most Common Natural Colloid,
 Constitutes 50 - 60% Of All Plasma Proteins ,
 Acidotic (Ph 6.9).
 Transport Of Many Small Molecules In The Blood ( Bilirubin, Calcium,
And Magnesium),
 Contributes For 75% To 80% Of The Normal Osmotic Pressure,
 Maintenance Of Body Plasma Volume.
 By The Liver & A Half-life 15-20 Days In The Body And 2 Days In
Plasma.
 Usually Used In Combination With Crystalloid Fluids.
 2.5 - 5 Gm Per 100ml Of Priming Solution

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Albumin
 5% albumin solutions (50 g/L or 5 g/dL) have a colloid osmotic pressure
of 20-29 mmHg and thus is similar in oncotic activity to plasma.
 25% albumin solutions (250g/L or 25 g/dL) have a colloid osmotic
pressure of 70-120 mm Hg . Degree of
 The oncotic effects of albumin last 12 to 18 hours.
 Albumin heated to 60°C for 10 h and then sterilized by ultrafiltration
 no risk of viral transmission.
 minimum side effects like allergic reactions, anaphylactoid reactions
and coagulation abnormalities compared to synthetic colloids.
 expensive as compared with other colloids.
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Priming Influence in Hemostasis

 A large volume of crystalloid priming increase of

platelet aggregation and a decrease in
circulating antithrombin III.
 Colloids solutions impaired platelet
adhesiveness during the bypass period and
decrease in von Willebrand factor & factor VIII .

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PRIMING STEPS FOR CARDIOPULMONARY
BYPASS CIRCUITS

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Filling the Reservoir:

 A- Check the priming you want to use for sterility, and make sure their
containers are not open or damaged .
 B- Fill the Hard-shell Reservoir with priming fluid through the quick
prime port by gravity via any of the filtered inlet ports located on the
top of the reservoir.
 C- Heparin should be injected into the reservoir at a rate of 2000-
3000 units per litre of the prime to ensure adequate anticoagulation.
If you administer blood with priming add 6 U Heparin to each 1 ml
blood added on priming .
 D- Add a sufficient prime to the system to maintain a dynamic priming
volume.
 E- It is extremely important, that the priming of the oxygenator and
circuit is administered per manufacturer's instructions for use.
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Recirculation:
 A- Put a clamp on the arterial and venous line after A-V shunting .
 B- Place clamps on either side of the arterial filter (If it was used).
 C- Unclamp the recirculation line between the membrane and the
reservoir.
 D- Turn on the blood pump to a slow speed to flush the priming fluid
through the venous reservoir, blood pump, and membrane
(oxygenator).
 E- When the circuit appears to be clear of bubbles, the pump speed
should be increased now to remove any bubbles within the circuit.
 F- The reservoir should be inspected for obvious bubbles and tapped to
remove them, and continue de-bubbling from the outlet of the
reservoir, head pump, membranes and progress to the arterial line , A-
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V shunt ,to venous line.

 Recirculation:
 G- Close the recirculation line between the membrane and the reservoir.
 H- Stop the pump slowly. Clamp the A-V shunt line.
 I- Start the priming for the arterial filter by releasing the lower
clamp(filter outlet), and turning on the blood pump at slow speed to
allow the primer to fill the filter retrogradely, and discharge air through
the purge line .
 J- De-air the pressure line .
 K- Stop the pump .Release the clamp from the A-V shunt line.
 L- Release the top clamp on the filter(filter inlet).
 M- Clamp the arterial filter bypass loop.
 N- Start the pump at high speed . Invert the filter and tap to remove
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bubbles.
Priming the A/V Loop
 A- Stop the blood pump.
 B- Clamp the A-V shunt line.
 C- If necessary, add more priming fluid to the venous reservoir.
 D- Unclamp the venous line. Unclamp the arterial line.
 E- Set occlusion of the arterial pump (if a roller pump is used) before
priming the A/V Loop. (See Occlusion Settings In Page 163)m
 F- Start the blood pump gradually.
 G-When all air is purged from the A/V loop, slowly increase blood
pump flow to high speed, and recirculate the priming fluid through
the entire circuit.
 H- Partially occluding the venous line is recommended to offer
resistance, to provide a positive pressure( around 80 mmHg) during
recirculating the primer, to remove any bubbles from the membranes
and filters. 33
 I- Before cutting the circuit by the scrub nurse, a final check must be
done by both the perfusionist and scrub nurse for the presence of
bubbles.
 Note: Before priming, a CO2 flush is recommended to displace air and
reduces the risk of gaseous emboli.
 Note: Pre-cardiopulmonary bypass filter use, is a recommended by
the manufacturer’s to remove particulate contamination from the
circuit.
 Warning: All gas emboli must be cleared from the extracorporeal
circuit before beginning bypass. Gas emboli are dangerous to the
patient.
 Warning: During recirculation do not use pulsatile flow, and do not
stop the pump suddenly. Otherwise gaseous emboli may enter from
gas phase due to inertia force. 34
Pre-warm the Priming Fluid

 A. Start heat exchanger water flow to pre-warm

the priming fluid.
 B. Inspect the entire system for leaks.

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Priming cardioplegia if demanded:
 A- Check the vials of cardioplegia before injecting in 500 ml normal
saline 0.9% bag.
 B- The bags must be labeled clearly with the date ,concentration ,and
name of the person who prepared it, immediately after preparation.
 C- Turn on the cardioplegia pump slowly to prime the cardioplegia
circuit with NaCl 0.9%.
 D-When the circuit appears to be clear of bubbles, the pump speed
should be increased to remove any bubbles within the circuit.
 Warning: Make sure that the flow of arterial pump is always higher
than the flow of cardioplegia pump.
 E- Check the cardioplegia pump calibration, and make sure it is
correctly programed into the pump console .
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Priming a centrifugal pump if demanded:

 A- Clamp the outlet tube of the venous reservoir .

 B- Prime the reservoir.
 C- Release the clamp on the outlet tube slowly to allow
the prime to fill the cones of the centrifugal head slowly(
by gravity).
 D- Check the cones for bubbles and if bubbles are found
,they should be let out of the inlet port back into the
venous reservoir .
 E- Insert a bi-directional flow probe into the arterial line.
 F- Turn on the centrifugal head motor gradually ,and
circulate the priming fluid through the entire circuit. 37
Thanks

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